erc20-demurrage-token-archive/README.md

RedistributedDemurrageToken

Use Case

• Network / Basic Income Token
  • 100 Sarafu is distributed to anyone in Kenya after user validation by the owner of a faucet which mints new Sarafu.
  • Validated users are those that validate their phone number in Kenya
  • A monthly Sarafu holding tax (demmurrage) of 2% is recorded as a demurrageModiifer.
  • Supply and user actual balances stay the same but are displayed minus the demurrageModiifer.
  • Each month the total amount of demurage is distributed out to users active and the demurrageModiifer for each user is reset to zero.
    • a single transaction is considered active (heartbeat).
  • This is meant to result in a disincentivization to hold (hodl) the Sarafu token and increase it's usage as a medium of excahnge rather than a store of value.

Inputs to Constructor (Set only once during contract deployment)

• 'Decay amount' (ppm) and period (blocks) is set at deploy time.
  • Cannot be changed
  • aka a holding Fee: A percentage of a users balance that will be charged and eventually redistributed to active users
• Demmurage Period: The time frame over which a new Holding Fee is applied and redistributed.

Ownership

• Contract creator is owner
• Ownership can be transferred (also to ownership void contract to make permissionless)

Mint

• Owner can add minters
  • A faucet contract would be a minter and set the amount of tokens to mint and distribute to new (validated) users.
• Minters can mint any amount

Demurrage

• Tax is applied when a mint or transfer is triggered for first time in new period;
  • Supply stays the same.
  • Updates demurrageModiifer which represents an exponential decay step (of size 'Decay amount' and is a a percentage of user balance)
    • demurrageModifier(i) = 'Decay amount' x demurrageModifier(i-1) x user balance
• All client-facing values (balance output , transfer inputs) are adjusted with demurrageModifier.
• Edge case: approve call, which may be called on either side of a period.

Redistribution

• One redistribution entry is added to storage for each period;
  • When mint is triggered, the new totalsupply is stored to the entry
  • When transfer is triggered, and the account did not yet participate in the period, the entry's participant count demurrageModifier is incremented.
• Account must have "participated" in a period to be redistribution beneficiary.
• Redistribution is applied when an account triggers a transfer for the first time in a new period;
  • Check if have participated in period.
  • Balance is increased by (total supply at end of period * demurrage modifier ) / number of participants
  • Participation field is zeroed out.
• Fractions must be rounded down (TODO)
  • Remainder is "dust" and should be sent to a dedicated "sink" address (TODO)

Data structures

• One word per account:
  • bits 000-159: value
  • bits 160-255: period
  • (we have more room here in case we want to cram something else in)
• One word per redistribution period:
  • bits 000-055: period
  • bits 056-215: supply
  • bits 216-253: participant count
  • bits 254: Set if invidiual redistribution amounts are fractions (TODO)
  • bits 255: Set if "dust" has been transferred to sink (TODO)

QA

• Basic python tests in place
• How to determine and generate test vectors, and how to adapt them to scripts.
• Audit sources?